W: GPG error: http://toolbelt.heroku.com/ubuntu ./ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C927EBE00F1B0520 code example
Example: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6494C6D6997C215E